Hey guys been a little while since I posted here last. Anyway I have been playing LSPDFR a lot and I notice when I get into Los Santos coming from I think th Olympic free way from Blaine county the fps drops to like 15-17. I borrowed my friends GTX 970 to replace my GTX 590 and in every other game and even vanilla GTA V without plugins running I get a solid 60 fps (except for gta I get like 40-60). I was running my plugins, drove into the city then used the console to unload all plugins and instantly butter smooth fps again. I just ordered a GTX 1060 6GB to replace my GTX 590 since Im not keeping my friends 970 and the 1060 is better anyway. I know my system is incredibly old running on a 9 year old CPU (Q9450) so I was about to build a new one but I asked my friend if I could use his GPU boy am I glad I did. I spent $230 on a new graphics card instead of over $1000 on a new PC. I can even run GTA V on the highest settings which like I said nets me 40-60 FPS which is insane for my machine. Anyway does anyone know why there is such an FPS drop while running plugins?

Plugins are processor-intensive so, if you have a lot of them, a new graphics card won't help.  A better investment would be a high-end Intel overclocked to 4+ GHz, but with the motherboard and cooling equipment you can easily spend way too much.

Some old plugins are poorly optimized too and will kill your frame rate no matter what your specs are.  Stuff like Keep Calm, Entity Persistence, anything that creates a lot of ambient events will slow down the game.

Interesting didn't know that about some plug ins. I don't have any of the ones you specified though but perhaps another one I have is the killer one. I do agree with your investment idea there but all socket 775 cpus are not really worth buying (I bought the q9450 a few months back for $25 up from a q8400 I bought new. Did it for the cache improvement). I'm really screwed either way when it comes to either graphics or CPU. If I were to build a new rig and keep the gtx 590 I would be stuck with dx11 and 5 year old performance and insane heat and power consumption. The GTX 1060 is a cheaper band aid for me which seems to net a lot of gain with not a lot of cost. My only real other issue at this time is my mother boards max of 8GB of ram. While playing black ops 3 at times I'm hugging 7gb usage. 

Very few games actually take advantage of DX12. The GTX 590 itself is a decently powerful card, even to todays standards. I'd say build a Skylake PC and upgrade the GPU once you can.

I know you said without plugins it runs fine but I have recently had massive problems with fps.

My specs are:

AMD FX-8350 8-CORE

16GB RAM

GTX 960

WIN 10 64BIT

I completely started again to try and fix the problem, reinstall windows, newest drivers, did have 8GB ram but thought it would help to get more, it did not. Loaded up gta without any mods just the base game and still getting drops to around 12fps. Can anyone confirm that it is rockstar that has ruined the performance of the game? I'm gutted I can't play lspdfr anymore it just gets unbearable.6 months ago I could run gta on very high setting and it ran PERFECTLY.